Suggestions for making a pattern for rounded leg padding? (without using foam)

I will be using either Matrices' method or the draping method to achieve leg padding; my only concern is how to make a paper pattern for padding pillows with a ROUNDED top, as I have seen. I know I could just buy 2-inch foam, shape it, then tape it up to get the pattern, but I'm on sort of a tight budget and have spent a lot on foam already.

If I could get some suggestions on patterning, that would be great!

Thank you for your time.